In many applications, where there is a need to remove existing concrete from vertical or inclined surfaces, particularly at elevated heights, it is necessary to attempt the removal manually with jackhammrers. However, many concrete encased installations may not be compromised by the microcracks such as those imparted by the severe mechanical impacts of a jackhammer. Hydrodemolition with high-pressure water jets would be ideal if there were a way of building a robot that could traverse the vertical or inclined surfaces. Attempts have been made to construct a vertical track over which a carriage supporting a nozzle with a high-pressure water jet travels. To speed up removal, two nozzles emitting water jets traveling together side-by-side across the carriage and back again were used. One problem that developed was the fact that less concrete is removed at the extreme of travel at either end because the second jet does not overlap the path of the first at each such end. This means that the periphery on each side will be stepped. This step must be removed manually.
Another problem arises from the thickness of the wall. Typically, nuclear reactor concrete housings have a thickness of the order of 4 feet. A system must be in place that allows the nozzles to travel up to 4 feet perpendicular to the track in order to remove the entire wall thickness of material. In addition, to prevent the nozzle housing, which is larger in diameter than the nozzle, from contacting the edge of the opening, a shorter lateral distance of travel would be required for each pass or each of a set of passes. The net effect would be a side edge that stepped towards the interior of the opening with increasing depth.
Accordingly, it is an object of the invention to provide a hydrodemolition machine having water jet assemblies that removes concrete material from an inclined concrete wall at a faster rate than known methods and devices.
It is a further object of the invention to provide a hydrodemolition machine with water jet assemblies that can create an opening in a thick concrete wall that is vertical or inclined without steps in the sides of the opening.